A screw compressor squeezes air between two rotors that mesh like a screw. Use the view to look inside and follow a pocket of air from the suction port, along the meshing lobes, to the discharge.
A screw air compressor squeezes air between two spiralling rotors instead of a piston. The rotors look like a pair of intermeshing screws â one with convex lobes, the other with matching grooves â turning inside a figure-of-eight chamber. Air is drawn in at one end, closed into a pocket, and carried along while the pocket gets smaller.
From outside, a screw compressor is just a box with a pipe in and a pipe out. All the action happens in the tiny gap between the two rotors, so a cutaway is the only way to see how the profiles mesh and how a pocket of air is sealed, carried and squeezed.
As the two rotors turn, the space between their lobes opens up at the suction port. The pressure there drops, and outside air flows in to fill the opening pocket.
The convex lobes of the male rotor slide into the concave grooves of the female rotor. Once the rotors turn past the suction port, the pocket is closed off, with a fixed amount of air sealed inside.
The mechanical profile of the rotors carries the pocket along the length of the screws. Because the threads are shaped so the pocket gets smaller, the same air is squeezed into less space and its pressure climbs.
When the pocket reaches the discharge port it has reached the working pressure, and the air is pushed out into the pipework. Because several pockets overlap at once, the output is a smooth, steady flow.
A pair of timing gears at the rotor ends locks the shafts at a fixed angle, so the lobes and grooves never touch. Bearings at each end carry the shafts and let them spin fast with very little friction.
It traps a measured pocket of air between two meshing rotors and then shrinks that pocket. As the pocket gets smaller along the rotor length, the same amount of air is squeezed into less space, so its pressure rises.
One rotor has convex lobes and the other has matching concave grooves. Together they form a moving seal, like a screw thread, that stays tight while the male rotor turns faster than the female rotor.
No. A pair of timing gears at the ends locks the shafts at a fixed angle so the lobes and grooves mesh with a fine clearance but never rub. That is why screw compressors can run for a long time without wear on the rotors.
A piston delivers air in pulses, once per stroke. A screw rotor overlaps its pockets, so it pushes out a steady, continuous flow with far less vibration and noise.
The housing forms the figure-of-eight chamber around the rotors and holds the suction and discharge ports. It keeps every pocket of air sealed as the rotors carry and squeeze it.